<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>canvas 动画循环</title>
  <style>
    canvas {
      border: 1px solid #999;
    }
  </style>
</head>
<body>
  <canvas id="canvas" width="80" height="80"></canvas>
</body>
<script src="./app.js"></script>
</html>